As one of the 8 highlight papers selected for the 2010 Symposium on VLSI Technology, Macronix International is presenting a paper demonstrating the fabrication of an 8-layer, 75nm half-pitch, 3D VG (Vertical Gate) NAND Flash using a junction-free BE-SONOS device. Macronix claims this technology provides a successful path to the most scalable and most efficient 3D NAND Flash using its patented BE- SONOS (barrier engineering) charge-trapping technology and 3D decoding architecture.

"Traditional NAND Flash will be facing technology barrier when it scales to below 2Xnm node," said C. Y. Lu, President of Macronix. "The three-dimensional memory cell array structure has been proposed to be the most promising candidate for NAND Flash to shrink to below 1Xnm. Macronix's 3D memory research results based on our own BE-SONOS technology have set a new milestone for next generation NAND Flash to meet high density capacity requirement."

Several 3D NAND Flash structures have been proposed, such as P-BiCS (Pipe-shaped Bit Cost Scalable), TCAT (Terabit Cell Array Transistor), VSAT (Vertical Stacked Array Transistor) and VG (Vertical Gate). However, according to Macronix, in a 3D structure interference (cross talk) occurs not only between neighbouring cells in the same plane but also between vertical neighbours in adjacent planes. This has become a new challenge in addition to the conventional Moore's law scaling issues.

Through detailed analyses on scalability, reading current (which determines read speed performance) and cross talk, Macronix's work has chosen the VG architecture, believing it is the best approach. Simulation work showed this structure could be scaled to 25nm node in a 3D array, providing density far beyond conventional 2D NAND Flash.